#include<bits/stdc++.h>
using namespace std;
int main(){
    int i=1,n,h=0,j,b; 
    cin>>n;
    for(i=1;1<=n;i++){
    	j=i;
    	if(1%5==0){
    		while(j>0){
    			b=j%10;
    			j=j/10;
    			if(b==5){
    				h++;
    				break;
    			}
    		}
    	}
    }
    
	return 0;
}

/**************************************************************
	Problem: 1057
	User: zhenghaoxuan
	Language: C++
	Result: Wrong Answer
****************************************************************/